Many vector datasets are created from remote sensed imagery. If the conversion processes does not remove the “steps” in the boundaries of the created polygons the data can not only look “unreal” it can also greatly increase the complexity of the resultant polygons (and thus the number of vertices and size of the stored object)Read More
The Oracle Locator/Spatial SDO_RELATE search operator, and convenience operators, all provide for the ability to search for a positive occurrence of a topological relationship: Operator Description SDO_RELATE Determines whether or not two geometries interact in a specified way. SDO_ANYINTERACT Checks if search and target geometries have the ANYINTERACT topological relationship. SDO_CONTAINS Checks if search andRead More
One often meets a question like this (asked on the PostGIS discussion list) about the performance of raster images: Can anyone comment on the “Performance” of the PostGIS Rater or WKTRaster? If you were to serve this onto a web application, how effective are they? Well, I’m talking of very large datasets like 10GB eachRead More
There is often a need for all sorts of reasons, for the generation of spatial data within a database like SQL Server 2008. I have blogged on this before for Oracle Locator/Spatial but the tricks to doing this in SQL Server 2008 are very much different from what is achievable in Oracle. This is toRead More
I was contacted recently by someone who wanted to know: I am struggling to create a function where I can take multiple x and y columns and create a geometry from that. I have already created such an function for points. Attached is some of the rows within the table. As you can see thereRead More
I have always had an interest in the possibilities that concave (not convex) hull geometries provide for geoprocessing (not just in databases). There is work going on by Regina Obe to create a concave hull function for PostGIS. In addition, there has been some great work by Glenn Hudson and Matt Duckham in creating anRead More
There is a discussion going on on LinkekIn about GIS and cloud computing. I responded to the posts and include my comments (which should be read in light of the threads themselves) as follows. The reason is because I have been thinking about the failure (or silence) about whether any update functions (eg the variouslyRead More
Just had need to turn project only the 2D (X/Y) ordinates of a DIMINFO value from USER_SDO_GEOM_METADATA into a project different from its current value. The original values are: Here’s the SQL I used to do it: Hope that helps someone out there. (A lot of these ideas is being wrapped into GeoRaptor. Download andRead More